The present invention relates to a plant growth regulator containing as the active substance one or more N-substituted alanine derivatives, especially an agent which is effective to control suckers of tobacco plant.
Some of the N-substituted alanine derivatives to be used as the active substances in the present invention are novel and others are known compounds. It has been known that some N-substituted alanine derivatives are useful as herbicidally active substances as disclosed in Japanese Patent Laid-open specification Sho No. 52-15821 (corresponding to British Pat. No. 1547758) and U.S. Pat. No. 4,102,671. However, it has not heretofore been known that the derivatives are useful as agents for controlling suckers of tobacco and young shoots of woody plants.
Most of the compounds of the present invention have strong auxin activities. It has been known that when a compound having strong auxin activity is applied to plants, abnormal growth, serious malformation, or withering actions are often exhibited. Therefore, the compounds are generally used as herbicides for killing undesirable weeds.
It has been unexpectedly found that some compounds which have strong auxin activities can effectively control young shoots of woody plants and suckers of tobacco plant while causing substantially no adverse effect on the plant growth and the yield of tobacco in practical use, thus the present invention has been accomplished.